1. Field of the Invention
The present invention relates to a method of controlling power in an optical disc apparatus, and more particularly, to a method of adjusting record and reproduction power without using a component for measuring power of emitting light of a laser diode in an optical disc apparatus.
2. Description of the Related Art
An optical disc apparatus records data or reads data recorded at an optical disc by radiating light emitted from a laser diode to the optical disc. In the optical disc apparatus, while recording data or reproducing data, an internal temperature changes and an operation condition of the laser diode is changed according to a temperature change and thus in order to enhance a data record quality or a data reproduction quality, power of output light of the laser diode should be constantly maintained or should be maintained in a desired level.
FIG. 1 is a diagram illustrating a method of constantly maintaining laser power using a conventional Front Monitor Diode (FMD).
The optical disc apparatus adopts an FMD separately from a laser diode (LD) to monitor light output from the laser diode and constantly adjusts light regardless of an internal temperature based on the monitored light. The FMD detects and outputs laser power which the LD presently outputs, and a Digital Signal Processor (DSP) performs A/D conversion of an output of the FMD and converts present laser power to a DAC value, which is driving data that drives the LD, compares the DAC value with target power, calculates a power reduction amount, performs D/A conversion of the power reduction amount to a current, applies the current to the LD, compensates an output power change of the LD according to a temperature change, and maintains output laser power to a target value.